Electric furnace for glowing metal bands by induction currents



Oct. 30, 1928.

' M. TAMA ELECTRIC FURNACE FOR GLOWING METAL BANDS BY INDUCTION CUNRENTS 4 Sheets-Sheet 1 Filed Nov. 29, 1927 Oct; 30, 1928.

y M. TAMA ELECTRIC FURNACE FOR GLOWIN METAL BANDS BY INDUCTION CURENTS 4, Smets-Sheet 2 Aas@ Java/22er: Y War/zus? v-moz y by M21/ orf-vraag y Oct. 30, 1928.

ML TAMA ELECTRIC FURNGE FOR GLOWING METAL BANDS BY INDUCTION CBRENTS Filed Nov. 29, 1.927

4 Sheets-Sheetv 5 Jive/zio?? v .Manuel ma Oct. 30, 1928..

M.'r TAMA IELcTRrc: FURNACE Fon GLowING uE'rAL `15A-rms BY INDUCTION cURRENTs t SheetsSheet 4 Filed Nov. '29. '1927 Patented Oct. 30, 19:28.

UNITED A STATES PATENT OFFICE.

MANUEL TAMA, or Mnssnvownnxn, NEAR EBERSWALDE, annuity.

'ELECTRIC FURNACE FOR GLOWING METAL BANDS BY INDUCTION CURB-EMS.

" 'Application nieu November 29, i927, serial' No. 236,505, and in Germany september 17, 1927.

When manufacturing sheetnietal or metalbands it is customary to roll plates of comparatively great weight to strips which have -rolling operation. The annealing of the 'respect to it.

ununiformly.

wound-up strips which is necessary either aft-v er every rolling operation or at least after a certain number thereof is effected by inserting the rings or coils into annealing boxes or, as is also done often times, into gas-tired inuflie furnaces, but as the diameter of the metal-strip rings or coils is considerable and their weight is greatit is dihciilt to obtain a uniform temperature throughout the entire bulk of metal.` In most cases the outer portions are heated too strongly and the inner ones not strongly enough.

It has already been proposed to pull the metal-strips through a heated chamber, win ding them olf a reel located outside of one end of the heating chamber and winding them on again on a reel provided outside the other end I of said chamber b ut this procedure is uneco nomical because alarge radiating surface is required and the therinic efficiency is low.

Another proposal has been to heat the metal strips by electric induction, the strips being employed as secondary conductor of a transformer, but the lmeansdesiigned for this purpose proved unsuited for it,`as iron-coupled transformers were used, the iron core forming an obstacle for inserting and withdrawing the rings.

The present inventionovercomes this drawback by making use of av so-called air-trans former, that is to say a transformer without an iron core so that the furnace consists chieliy of-two" concentric coils, viz an outer stationary solenoid and the metal-ring introduced into this solenoid and lying concentrically with The electric current induced in the metal coil to be annealed is so-to-say forced outwardly by reason of the Askin-effectl that is to say, there {iows a stronger current in the outer layers of the metal-coil than in the inner layers so that the ring is heated It is known that the skin-effcct, in other words: the depth of penetration, depends upon the frequency'of the current, as well as upon the conductivity of the metal treated and the permeability of the same. Tests have vs hown that for the sizes 01' dimensions occurring 1n the metal industry,

p ones, but as is known,

'quency of from 50 to 6() present in the furnace;

especially as regards the annealing of brass strips and sheet-brass, a frequency of from to 60 cycles per. second is particularly suited. With these frequencies a uniform heating of the ring to'be annealed is obtained if the dimensions of the ring are the usual there takes place at said number of periods a rather considerable lagging between the current and the voltage whereby the power factor is reduced. This phase-lagging can, however, be reduced by connection up to the circuit condensers or other means known in electrotechnics for the purpose stated. The employment of a fre cycles presents, besides, the further advantage that no separate frequency transformer is required.

Carrying through the invention is effected most practically in this manner that the metal rings to be annealed are wound upon a drum which then is inserted into the solenoid coil,

particular provisions 'being made to prevent the drum itself from *cally and by way of examples on the accompanying drawings on which Figure l is a being heated which vertical section through an electric furnace designed according to this invention, the drum with the metal-strip thereon being just Figure 2 is an axial section through another form of the drum alone, Figure 3 is a plan of the drum shown in Figure 2; Figure 4 is a vertical section through a modification of the furnace, and Figure 5 is a plan of this modification.

In Figure l of the drawings 1 denotes the primary coil which is Wound in the usual manner either of flat copper strip or of flattened copper tube.` This latter'foi'm is made use of when cooling by water is necessary. The layers of the windings are insulated from one another by suitable insulating material, for instance asbestos, micanite, or the like. The coil l is clamped fast between two flanges Zand 3 by bolts 4, and lined interiorly with a ring 5 of an insulating materie l. The solenoid formed in this manner constitutes the exterior cylindrical shell of the heating or annealing furnace. Vithn this shell, in the lowermost portion thereof, is a layer 6 of a refractory material which forms the bottom of the furnace, and centrally from this bottom extends upwardly an axle-forming member 7 which has a pointed upper end 8 and upon a space 12 for the reception of the counter! welght 11 when the cover 9 4is lifted. It is,` of Course, as Well possiblev to place the furnace directly upon the ioor.

In order to close the furnace perfectly tight, al waterseal 13 may be provided, as'

shown, and it is in' .this case practical to arrange the water-seal eccentrically with respect to the cover 9 in order -to prevent any vdisturbance of the proper upward and down# ward movement of the cover.

The cover 9 consists of a casing or shell 14 of a non-magnetic metal, and of a filling of a'refractory. material.

casing or shell 14. in order to obviate a dis- .turbance in the l formation of the field. Chrome-nickel alloys are best suited for said `casing or shell, the more so since the resistance to heat is very. great.- The cover is prol vided with a non-return valve 15 permitting the air enclosed in the furnace and expand ing in a hot state to escape. Also an inspec-v tion channel 16 closedwith refractory glass is provided in the cover.

The material 17 to be annealed is coiled' upon a separate drum. It is located in close proximity to the insulating wall 5 in order to bring about a possibly good coupling'between the primary and the secondary coil.' For the same reason a high-grade insulating material is used fo1 the wall 5 so that this latter need have only a slight thickness, and the primary and the Vsecondary coil can lie in close proximity to one another.

The thickness of the ring 17, that is to say, of the superposed turns forming it, is such that with the known conductivity of the metal to be annealed and with the known frequency of the current the depth of penetra tion of the'induced current is either equal to, or greater than, the thickness of the secondary coil.

The drum comprises chiefly an upper. and

a lower hub. 18 fand 19. connected with each other by 'a sleeve 20. The sleeve is shoved upon the vertical. axle 7 The hubs 18 and 19 are preferably -made integral with disks (or spoke-stars) 18* and 19, of which the upper is connected with a flange 23 of an'- ,gular section and the lower with a flat fiange 22, and these flanges are connected with each other by bolts 21 passing also through the disks or spoke-stars 18* and' 19, All these It is important toI make use of a non-magnetic metal for the however, an actual cylinderbut com members are enclosed in a sheet-metal shell 24:. and its projecting portion 25 serves as support for the coiled metal strip` to lowed. Y

When the annealing procedure has been finished, the cover 9 is swung upwards,.where after the drum .Withthe metal coil is lifted out of the furnace by a crane or-the like. Then another drum with another section of metal-strip to be annealed isinsertedinto the furnace, this latter isagain closed,- and another annealing procedure is carried through.

In order to preventthe drum from being heated'also, which-would cause a loss of heat, it is made of a material of a greater electric resistancev than the metal-strip to be annealed. It may also be subdivided into 'parts f in such a manner that no closed path for the` secondary current exists within it. I f the furnace is employed for the annealing of brass it is suicient to make the drum. of

wrought-iron in which case-it will not become excessively hot. 1.

Owing to the ununiform heating of the drum and the metal-strip and to thedifferent coeflicients of expansion of these two parts, if they are made of different materials, the metal-strip coil to be annealed will expand more strongly than the drum and will consequently move off the drum correspondngly. Butthis takes place not uniformly, as has been' discovered by way of tests; in fact, the material just being annealed moves olf usually at certain places and remains-at other places in contact with the drum, in consequence whereof the strip becomes on doyant. It also occurs that the individuaL, layers or turns separate from one another. Inthiscase it occurseasily that sparks jump 'over and destroy the metals at such places,

at all events atthe surface of the same. It is, therefore, necessary to provide means for preventing such occurrences, that is to say,- to keep the windings of the metal-strips, in close contact with one another, and the entire. strip in close. contact with the drum: A means for this pur ose consists in binding the metal-strip coil gast to the drum-by wire 17a or 'the like, but it is possible as -well to design the drum in such a manner that its diameter is mechanically increased during the annealing procedure inorder to follow the increase of the diameter of the Vcoiled metal-strip as it is annealed. i

A drum designed in this manner' is illustrated in Figs. 2 and 3. The two hubs 26. and 27*L are connected with each other by a. sleeve 28, and are preferably made integral with disks 26 and 27 rovided with'flanges 30 and' 31. These mem rs are ractically the same as those in Fig. 1. The anges are'connected by bolts 29, as well as by a shell 32 which is not,f

o eight segments designated32, 32", 32, 32, 32,

322 32S, and 32h'. The'ivertical of the segments are bent inwardly and contact with -eachother, and each of them is capable of a certain slight 'radial Vmovement, being then guided by the appertaining contacting vertical rims. Each se ent is provided with two spaced vertical le ges 34 located about midway between the appertaining vertical rims and being connected with each otherby a bolt 35. I have shown this arrangement and combination of parts in Figs. 2 and 3 only in connection with the segment 32, but also all other segments are designed in zjust the same' manner.

c The bolt 35 serves also for connecting the segment with an arm 36 which, in the'constructional `form* shown asv an example, is forked. The two legs forming the fork are stiffened with respect to oneanother by a bolt 37. The inner end of the arm 36 is hinged to a weight-forming heavy body 40 bearing upon aflange 41 of a sleeve 42 embracing thesleeve 28.- 'lhe sleeve 42 can' be shifted upon the sleeve 28, but it is also possible to couple the two sleeves with each other bya bolt43 which -follows: The metal-strip to be annealed is vcoiled upon the shell 32 and secured Vin its position in the above mentioned manner. Now

the bolt or pin43 which up to then h d coupled the sleeves28 and 42 with eachother is withdrawn and the drum (which must be supposed to be suspended from a crane with the aid of the hooks 44) is lowered d own intothe furnace, in such a manner, that the sleeve 28 slides down upon the axle 7 (Fig. 1). Now the chainsor ropes (not shown) Aof the crane are disconnected from the hooks 44, in consequence whereof the heavy member 40 presses the rods 36 outwardly, the action being practically similar to a toggle-joint lever, and

' owing to this action also the segments 32m-.32h

are'pressed radially outwards. The segments 1 follow the expansion ofthe metal-strip and keep it continually stretched, that is to sa the heavy member 40 holdsy it continual y under tension by the intermediary of the arm 36. In other words, the' diameter of the drum' increases in strict correspondence with the increase of the diameter of the metal-strip coiled upon the/drum.. -When the annealin procedure hasV been finished the crane c ams or ropes are again attached tothe hooks 44 (of which there are at least When then the drum is first the heavy member 40is Vthe .sleeve 28 by the pin or bolt 43, and the drum remains now contracted and receives another coiled metal-strip.

While in the constructional form shown in Fig. l the furnace is stationary and the drum receiving the metal-strip is vertically movable inforder to beinserted into, and removed from the furnace, Figs. 4 and 5 show a modication in which instead of the drum being vertically movable, the furnace-is movable.

There is, however, in this case -a plurality of drums, three in the example shown (Fig. 5) and each can co-operate withV said furnace.

In Fig. 4 45 denotes the primary coil and 46 a cylinderof an insulating material. vThe cylinder 45 is open at its lower end,.but closed at its top by a cover 47 48 denotes an outer shell enclosing the parts mentioned. A' rope 49 attached to the cover 47 :runs over a roll.

50 to a win'ch or the like (not shown), by means of which the furnace can be lifted and lowered along two standards 51 and 52 with the aid of Guide members, 54 and 55 projecting forth From thebottom flange 53 and the cover 47 as shown.

A rotary platform 56'is arranged approximately on a level with the iloor and can be locked lin the three positions corresponding to the three drums 57 shown in Fig. 5. These positions diier from one another by 120. In the Vone thereof A(righthand in Figs. 4 and v5) the metal-strip is coiled on and oil1 the drum. There is -ne'ar this place, righthand from it, a stationaryvertical pivot 60 which receives that drum (notl shown) with the metal-strip thereon which lcornes from the rolling mill,` and the metal-strip is then coiled from this drum ontov the drum 57. This latter 'drum is carried by a vertical pivot 58 connected with a horizontal cogwheel 59 driven'by any suitable mechanical or electrical. means (not shown) whereby the new metal-strip from the rolling mill Vis wound from the mill drum onto the drum 57, as already stated. There are three Vsuch driving devices (5 8, 59 etc.) carried'by a frame 62 providedwith rolls 63 running Vupon a circular rail 64, and there isconnected with the frame 62 a toothed ring 6l meshtermittently corresponding to the three po- 'ing with a co -wheel (not shown) driven insitions of therotary platform, as already Stated) by anysuitable'device. The arrow in Fig'. 5 indicates the direction of rotation of the rotaryplatform. When'a drum 57 with the metal-'strip thereonhas arrived below the furnace 45/46/47/48 this latter is lowered down upon that drum and the'annealing procedure is now carriedthrough. This having been effected, the furnace is lifted off the drum and the'platform 4is 4again turned for 120 whereby tliedrum with the annealed metal-strip is turned to that, place where itl can' cool down While thenext following metal- Coil is being annealed in the furnace.

There are obviously always three drums With-three metal-coils in course of treatment.

.While one drum With a metal-coil thereon is treated in thefurnace another drum receives band onto another drum, as Well as sufficient for the cooling down of themetal-coil rmovevd from the furnace. The constructional form shown in Figs. fand 5 renders, thus, possible, to Work practically continually and the primary coil of the furnace can be nearly continually traversed by the current'. The electric part of the plant can -be utilized, therefore, practically to its utmost capacity.

If a constructional form of the type shown in Fig. l is chosen it is practical to make use of two furnaces which are operated alternately so that also in this casca practically continuous service is maintained. While a drum with a metal-stripjthereon is treated in one of the two furnaces, the drum with a metal-strip thereon having been treated inother furnace is permitted to cool down in this latter 'Whereaftea this drum is removed and another is inserted, and vice versa. Of course, also these drums may be used' in connection with means for coiling the metal-strip from the rolling mill drums-thereon. There may be used simple reels with vertical axle 'for this purpose. Finally, instead of a rotary platform, as shown and described, a reciprocating platform may be used, and there may be provided on the one or the other type of platform 'a greater number of Udrums than three in order to prolong the time for the cooling down of the annealed metal-strip.

1. An electric furnace for annealing metal-l strips b induction current, comprising a drum a apted to receive the metal-strip to be annealed-and adapted to be wou'nd therearound; and a coilA adapted -to generate the induction current, said drum being adapted to he inserted into and removed from the. coil and forming with the metal-strip a transformer of which the metal-strip' forms the secondary coil for said transformer.

' An electric furnace for annealing metalstrips by induction current, comprising a drum adapted to receive themetal-strip to be annealed and ada ted'to be' coiled .therearound; and a coil a apted to 'form the primary winding -of atransformer/ and to generate the induction current, said metal-strip and drum forming` the secondary coil of the transformer.

3. An electric furnace for annealing metalstrips b induction current, comprising a drum a apted to receive the metal-strip to be annealed and adapted to be ycoiled therearound; and a coiladapted to form one of .the coils of a transformer and to generate the induction current, said metal-strip forming the other coil'of the transformer.

1f. An electric furnace for annealing metalstrips b Ainductioncurrent, comprising a drum a apted to receive the metal-strip to be annealed; means for holding the metalstrips in contact with the drum; and a coil adapted to form .the primary Winding of a' snips by'induction current, comprising a drumv adapted to receive themetal-strip to be annealed; a coil adapted to. form the pri-z mary Winding of a transformer and to gen` erate the induction current, said drum. and

metal-strip being adapted to be inserted into and out of the primary coil and forming the secondary coil of the transformer; a bot- 1 tom for closing said primary coil; and a pivot located centrally upon the bottom andadapted to receive and guide the'drum.

6. .An electricfurnace for annealing metal- 100 lstrips' by induction current, comprising a drum adapted to receive the metal-strip to be annealed; a coil adapted to form the primary vvinding of a transformer and togenerate the induction current,said drum and ,106'

metal-strip being, adapted to be inserted into and out of the primary coil and forming the secondary coil of the transformer; a bottom forclosing said primary coil; a pivot located centrally upon the bottom and adaptf 1.10

ed to receive ,and guide the drum; anda S'cover hinged to the primary coil and adapted to cover. the transformer.

7. An electriefurnace for annealing metalstri'ps by-induction current, comprising a 115 drum adapted-to receive the metal-strip to be annealed; a coil adapted toform the pri-l v mary winding of a transformer and to genv erate the. induction current, said drum and metal-strip being adapted .to be inserted into 12- andv out of the primary coil and forming the secondary coil of the transformer a. bottom for closing -said primary coil; a.4 ivot located centrally upon the bottom and a apted to receive and-guide thedrum; a cover 1 hinged to theprimary coil and adapted. to cover ,thetra sformer; and a. water; seal for the cover. A

8. An-electricfurnace for annealin metalstrips' by `induction current, comprising a drum adapted-to receive the metal-strip to be annealed and adapted to be coiled tl1erearound; and acoil adapted to form the pri'- mary Winding of a transformer and to generate the induction current, Said metalstrip and drum forming the secondary coil of the transformer and the electric conductivity of the metal of the drum being lower than the conductivity of the metal-strip.

9. An electric furnace for annealing metalstrips by induction current, comprising -a drum' consisting of tWo hubs, a sleeve connecting the hubs to each other, a sheet-metal cylinder adapted to receive the metal-strip to be, annealed, means for supporting the metal-strip uponA said cylinder, and means for cnnecting said cylinder with said hubs; and a coil adapted to forni the primary winding of a transformer and to generate the induction current, vsaid drum and metalstrips being adaptedto be inserted into and out of the primary coil and forming the secondary coil of the transformer.

10. An electric Vfurnace for annealing metal-strips by induction current, comprising a drum consisting of two hubs, a slee-ve connecting the hubsto each other, a. sheet-metal cylinder adapted to receive the metal-strip to be annealed, means for supporting the metal-strip upon said cylinder, means for connecting said cylinder with said hubs, and tension bolts for securingr the means and cylinder together; and a coil adapted to form the primary winding of a transformer and to generate. the induction current, said metalwstrip and drum forming the secondary' coil of the transformer and being adapted to be inserted into and out of the primary coil.

11. An electric furnace for annealing inetabstrips by induction current, comprising a drum adapted to receive the metal-strip to be annealed and being adapted to expand radially and a coil adapted to form tlie primary winding of a transformer and to generate the induction current, said drum and metal-strip being adapted to be inserted into and out of the primary coil and forming the secondary coil of the transformer.

12. An electric furnace for annealing metal-strips by Vinduction current, comprising a drum adapted to receive the metal-strip to be annealed kand having its Wall subdivided into segments; means for forcing the segments radially outwards to contact with the metal-strip; and a co'iljafdapted to form the primary Winding of ai"transformerand to generate the induction current, said drum and metal-strip being adapted to be inserted into and out of the primary coil and forming the secondary coil ofthe transformer.

13. An electric furnace for annealing metal-strips by induction current, comprising a drum adapte-d to receive the'metal-strip to be annealed and having its circumferential Wall subdivided into segments; a heavy body arranged centrally in the drum and adaptedto be moved axially; means for guiding said body axially; rods connecting said body With the segments, said body androds providing for contact of the segments with the metalstrip ;,and a coil adapted to form the primary winding of a transformer and to generate the induction current, said drum and metal-strip 4being adapted to be inserted into and out of the primary coil and forming the secondary coil of the transformer;

14.' An electric furnace for annealing metal-strips by induction current, comprising a drum adapted to receive the metal-Strip to be annealed and having its Wall subdivided into segments; a heavy body arranged centrally in the drum and adapted to be/moved axially; means for guiding said body axially; rods connecting said body With the segments; nienibers fixed to the body adapted to lift it and thereby draw the segments radially inwardly and away from the metal-strip; and a qcoil adapted to form the primary Winding of a transformer and to generate the induction current, said drum and metal-strip being adapted to be inserted into and out of the primary coil and forming the secondary coil of the transformer. y

15. An electric furnace for annealing -metal-strips by induction current, comprising a drum adapted to receive the metal-strip to be annealed; a primary coil adapted to generate the induction current, said metal-strip acting as a secondary coil for a transformer; and means for raising and lowering the primary coil over the drum and metal-strip.

16. An electric furnace for annealing metal-strips by induction current, comprising a drumadapted to receive the metal-strip 'to be annealed; a primary coil adapted to generate the induction current, said metal-strip acting as a secondary coil for a transformer; means for raising and lowering the primary coil over the drum ,and metal-strip; and a movable platform adapted to transport the drum and metal-strip.

17. An electric furnace for annealing metal-strips by induction current, comprising a rotary platform; a plurality of drums uniformly distributed on said platform and each being adapted to receive the metal-strip to be annealed; a primary coil adapted to generate the.-'f'iiiduction current, said metalstrip acting as a secondary coil for a transformer; means for rotating said platform with the drums and metal-strips; and means nature.

MANUEL TAMA. 

